Reversible circulation internal-fan kiln



June 9, 1925.

R. THELEN anvnasmm CIRCULATION INTERNAL FAN KILN Original Filed April 19, 1924 3 Sheets-$heet 1 Fig-1 INVENTOR. ROkF IHELQEN a ATTORNEYS.

' "June 9, 1925. 1,541,294

R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Original Filed April 19, 1924 3 Sheets-Sheet 2 M II. I

INVENTOR. Row Megan BY ATTORNEYS.

Fig-Z June 9, 1925. 1,541,294

- R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Original Filed April 19. 1924 3 Sheets-Sheet '3.

Fig-5 I N VEN TOR.

. OLF HELEN R 9 MA TTORNEYS.

Patented June 9, 1925.

1,541,294 PATENT OFFICE.

UNITED STATES ROLF TI-IELEN, OF MADISON, WISCONSIN.

REVERSIBLE CIRCULATION INTERNAL-FAN KILN.

Original application filed April 19, 1924, Serial No. 708,323. Divided and this application filed March Serial No. 14,422.

(GRANTED UNDER THE ACT OF MARCH 3, 1883; 22 STAT. I. 625.)

To (17! whom it may concern: I

Be it known that I, ROLF THELEN, a citizen of the United States of America, and an employee of the Department of Agriculture, residing in Madison, Wisconsin (whose postofiice address is Forest Products Laboratory, Madison, lVisconsin), have invented a new and Improved Reversible Circulation Internal-Fan Kiln.

This application is a division of an application filed April 19, 1924, which bears Serial Number 708,323.

This application is made under the act of March 3, 1883, chapter 143 (22 Stat. 625), and the invention herein described and claimed may be used by the Government of the United States, its officers and employees, and by any person in the United States without the payment to me of any royalty thereon. I hereby dedicate the same to the free use of the Government and the people of the United States.

My invention consists in an improvement in the design of forced circulation kilns or chambers for drying and conditioning lumber or similar material. However, its use is not limited to wood or wood products. It consists in the adaptation of fans of the disk type. or similar types, to the production of a unique internal circulation of air and the vapor in the kiln combined with the production and regulation of the heat and the humidity within the kiln.

This invention is illustrated in Figures 1 to 3. Figure 1 represents a longitudinal sectional elevation of the fan and adjacent parts, Figure 2 represents a horizontal section taken at varying elevations at and below the rails. Figure 3 represents a crosssectional elevation.

The principal feature which I claim as novel and an improvement over existing kilns is the use and arrangement of the fans and the air. distributing system. This arrangement is such that a very fast and uniform circulation of air and vapor through the piles of lumber may be secured and it permits the periodic reversal of the direction of the air movement by simply reversing the direction of rotation of the fans. The air distributing system provides a very uniform flow of air throughout the length and breadth of the kiln and eliminates the nonuniformity of drying, which is one of the commonest troubles experienced in the ordinary kiln. The arrangement of the fans upon two shafts extending throughout the length of the kiln provides a simple means of producing a brisk circulation; and the elimination of comparatively small ducts such as those used in external blower kilns reduces very materially the work required to produce a given circulation. The differences in air pressure required in the operation of this kiln are much smaller than those ordinarily required in kilns employing centrifugal blowers, and the disk fans operate very efficiently at these low pressures. Measurements recently made indicate that the static pressures necessary for the successful operation of this system are materially less than one-eighth of an inch of water pressure. It is possible, therefore, by the use of this invention to produce a very great and uniform circulation of air and vapor within the kiln with a very small expenditure of power.

While it is obvious that there are many possible ways in which the use of internal fans can be adapted to.dry kilns of different types, this invention is limited to double track kilns in which the lumber is edge stacked. In edge stacked lumber the width of each board is in a vertical directlon, the thickness and length being in horizontal directions.

Any well-known means of heating the air and the vapor in the kiln may be used in conjunction with this invention. When steam pipes are used they may be arrange-d beneath the lumber piles at the sides of the kiln or in any other convenient manner. Any convenient form and arrangement of heaters may be used.

The drawings show and the specification describes steam jet pipes for increasing the humidity, and air inlet flues and air outlet fiues with suitable dampers for decreasing the humidity.

While the drawings show and the specification describes specific means for heating the air and the vapor in the kiln and for regulating the humidity of the air in the kiln, this invention is not limited specifically to the arrangements described, but may make use of any other well-known and suitable means for accomplishing the same purposes.

- means for longitudinal motion.

While the drawings illustrateand the specification describes certain specifieforms of piling, the invention is not limited to these particular forms since it is equally applicable to other forms; neither is the invention limited to the specific form of rails, trucks, and track supports illustrated in the drawings and described in the specification.

Referring to Figures 1, 2, and 3, which are correspondingly lettered: AA represent the side deflecting partitions. These partitions serve to form a passageway for the air from the heating coils at the sides of the main air distributors to the fans and vice versa, the air moving in a more or less horizontal direction either inward toward the fans or outward from them, dependlng upon the direction of the rotation of the fans. BB are the fans producing the circulation. Straight-bladed disk. fans are preferable. Any type of fan, however, in which the reversal of the direction of rotation of the fan produces a reversal in the direction of the fiow of the air current passing through the fan can be used. CC are the shafts upon which the fans are mounted. Provision is made to take care of the expansion and contraction of these shafts with changes in the temperature in the kiln and to take care of the thrust of the fans. This provision consists in equipping one of the bearings II with suitable thrust rings or collars and equipping all of the other bearings II on each shaft with any well-known Plain bearings and roller bearings require no special provision of this kind. Certain types of ball bearings require housings which permit the entire bearings to slide longitudinally within them. DD are air inlet dampers used to regulate and control the amount of air entering the kiln from the outside. EE are the heating coils. These may be of the return bend type or other convenient type. FF are the steam jet pipes used to increase the humidity of the air in the kiln. Suitable openings are provided to permit the escape of the steam throughout the length of the kiln. Various other common and well-known arrangements may be used. GG are the lumber-supporting trucks. HH are the shaft hangers. II are the bearings for the shafts CC. J J are the tracks upon which the lumber-supporting trucks run. KK are the side. walls of the kiln. LL is the lumber to be dried. MM are the track supports. NN are the shaft pulleys. 00 are air outlet dampers for controlling the amount of air being exhausted from the kiln. PP are the belts passing over the pulleys NN and Q. Q, is the motor pulley. R is the motor which furnishes the power to drive the fans. S is the switch for controlling the speed and rotation of the motor armature. While the drawings show and the specification describes an electric motor, any other suitable driving means may be used. TT are air inlet fiues in which the I of lumber and the side walls of the kiln.

XX are the main air distributors. YY are the second diffusers. ZZ are the first diffusers. The plenum chambers between the second diffusers and the first diffusers are the secondary plenum chambers. bb are the fan housings and partitions. 0c and old are the plenum chamber partitions. 66 are the third diffusers. While the drawings show and the specification describes certain specific arrangement of the fans and shafts, this invention is not limited to this particular arrangement, since it is obvious that its functions can be performed in an equivalent manner with other arrangements of the fans.

The operation of the kiln is briefl as follows: The lumber is placed in the riln, the doors and all of the dampers are closed, and the kiln is started. Steam is turned into the coils and the steam jets are turned on. Suitable regulating devices are provided to control and regulate the supply of steam to the heating coils and the supply of the steam to the steam jets. If it is found impossible to reduce the humidity to the desired point with the steam jets all turned off, the dampers DD and-OO are opened to allow fresh air to enter and-moist air to escape. These dampers should be adjusted so that a humidity below that desired will be secured.

The steam jets may then supply a sufficient amount of steam to bring t e humidity up to the desired point. Assuming that the direction of rotation of the fans is such that the air and vapor move upward through the lumber piles LL they will pass downward through the central air passage V and the side air passages WW, over the heating coils EE, through the side deflecting partitions AA, through the fans BB, upward past the first diffusers ZZ, the second diffusers YY, and the third diffusers cc into the lumber piles LL. When the direction of rotation of the fans is reversed the direction of the circulationof air and vapor is likewise reversed. When the direction of the circulation of the air and vapor is upward through the lumber the various chambers between the fans and the first diffusers. between the first diffusers and the second diffusers, and between the second diffusers and the third diffusers, respectively, are un- 1 der slight pressure'and act as plenum chambers. The velocity of the air movement through these chambers is comparatively slow. The use of these plenum chambers and the various sets of diffusers in the manlil ner indicated produces a very uniform fiow of air through the length of the kiln. The unbalancing effect of the horizontal air flow produced by the fans is practically eliminated by allowing a slight ressure to build up in the main air distrlbutors. This is still further eliminated by the slight plenum in the space between the upper and lower distributors. It is obvious that the kiln would work reasonably well with single sets of diffusers for each main air distributor and that still further uniformity in air distribution might be secured by adding a third or even a fourth set of diffusers. The principle, of course, remains the same and practical expediency will determine the balance between increased uniformity of air distribution secured by the addition of more sets of distributors and the loss in efficiency which they cause. It is also obvious that any well-known form of distributor may be used. The invention is not restricted to the form illustrated in which the openings consist simply of spaces between the slats running the full length of the kiln.

When the direction of the circulation of the air and vapor is such that they pass through the diffusers and plenum chambers immediately after leaving the lumber piles instead of immediately before entering them, the air distributing system, which consists of the main air distributor, the side deflecting partitions, the plenum chambers and the various diffusers, .does not materially assist in producing a uniform circulation. The comparatively great length of air travel from the fans to the point at which the air and vapor enter the lumber has been found sufiicient to produr'e the desired uniformity in connectionwith the other features of the design. The arrangement of the heating coils may be made to assist in smoothing out unevennesses in the circulation. It has been found through experience with a great many different types of forced circulation in dry kilns that it is not possible to secure uniformity of distribution of the air and vapor if they be handled at high velocities. In order to produce uniform satisfactory circulation, it is essential that the air and vapor be moved at low velocities and that special means be provided for the uniform distribution of the air and vapor through the kiln. The use of internal fans and large plenum chambers produces this result, since the velocity of the air and vapor through the fans themselves is comparatively low and the velocity in the plenum chambers is so small that the velocity head can not be measured with manometers and similar instruments usually used for the purpose.

It is well understood that when the circulation of the air and the vapor in the kiln is continuously in one direction, that porber picks up moisture and thus reduces its drying capacity. The reversal of the direction of the air circulation overcomes this defect since that edge of each lumber pile which was the entering air edge before reversal becomes the leaving air edge after reversal. Those portions of the piles which dried fastest before reversal dry most slowly after reversal. The reversal of the circulation will in practice be done periodically every two or three days or oftener, the exact period being determined by the condition of the lumber in the kiln.

Several arrangements of the plenum chambers are possible and practicable. The principal object of the plenum chambers and diffusers is to produce a uniform flow of air and vapor through the lumber to be dried, and any detailed arrangement which will accomplish this result will be satisfactory if at the same time it does not con sume an excessive amount of power.

Having fully described the principles of this invention and the manner in which they can be embodied in a dry kiln, I claim as original:

1. In a double track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; and an air distributing system comprising side deflecting partitions, two main air distributors, and two sets of diffusers for each main air distributor.

2. In a double track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet fiues and dampered air outlet flues; and an air distributing system comprising side deflecting partitions, two main air distributors, and two sets of diffusers for each main distributor.

3. In a double track dry kiln arranged for edge stacking: two series of'fans; two shafts on which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet flues and dampered air outlet flues; means for heating the kiln and its contents; and an air distributing system comprising side deflectin partitions, two main air distributors, and two sets of diflusers for each main air distributor.

4. In a double track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation;

means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln ;dampered air inlet fines and dam ered air outlet flues; means for heatin 'the liiln and its contents; means for humidifying the atmosphere in the kiln; and an air distributing system comprising side deflecting partitions, two main air distributors; and two sets of diifusersfor each main air distributor.

5. In a double track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; a )lenum chamber for each fan; and a difuser with restricted discharge passages for each plenum chamber.

6. In a double track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet fines and dampered air outlet flues; a plenum chamber for each fan; and a diffuser with restricted discharge passages for each plenum chamber.

7. In a double track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet fiues and dampered air outlet fines; means for heating the kiln and its contents; a plenum chamber for each fan; and a diffuser with restricted discharge passages for each lenum chamber.

8. n a double track dry kiln arranged for edge stacking: two series of fans; two shafts on. which the fans are mounted for rotation; means for rotating-said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet fines and dampered airoutlet flues;

means for heating the kiln and its contents; means for humidifying the atmosphere in the kiln; a plenum chamber for each fan; and a diffuser with restricted discharge passages for each plenum chamber.

9. In a double track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal'of the circulation of the air and vapor in said kiln; a series of plenum chambers for each fan; and a diffuser with restricted discharge passages for each plenum chamber.

10. In a double track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet fines and dampered air outlet flues; a series of plenum chambers for each fan; and a diffuser with restricted discharge passages for each plenum chamber.

11. In a double track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet fines and dampered air outlet flues; means for heating the kiln and its contents; a series of plenum chambers for each fan; and a diffuser with restricted gischarge passages for each plenum cham- 12. In a double track dry kiln arranged for edge stacking: two series of fans; two shafts on which the fans are mounted for rotation; means for rotating said shafts in either direction to cause reversal of the circulation of the air and vapor in said kiln; dampered air inlet fines and dampered air outlet fiues; means for heating the kiln and its contents; means for humidifying the atmosphere in the kiln; a series of plenum chambers for each fan; and a diffuser with restricted discharge passages for each plenum chamber.

13. In a double track dry kiln arranged for edge stacking: two series of internal fans; a plenum chamber for each fan; and a diffuser with restricted discharge passages for each plenum chamber.

14. In a double track dry kiln arranged for edge stacking: two series of internal fans; a series of plenum chambers for each fan; and a diffuser with restricted discharge passages for each plenum chamber.

February 14, 1925.

ROLF THELE-i. 

